The role of gastroesophageal reflux in exercise-triggered asthma: a randomized controlled trial

BACKGROUND

Exercise-triggered asthma (ETA) develops when physical activity triggers asthma symptoms during or directly after exercise. In patients prone to symptoms of supra-esophageal reflux, exercise may trigger gastroesophageal reflux (GER), resulting in such symptoms.

AIMS

To determine the prevalence of abnormal pH in patients with ETA and to determine whether acid suppression improves symptoms in ETA patients.

METHODS

We performed a randomized double-blind trial of rabeprazole versus placebo in the treatment of patients with ETA. Patients underwent treadmill protocol to determine their VO(2 max). Next, pH testing was initiated while undergoing a 30-min treadmill program exercising them at 65% of their VO(2 max). They were subsequently randomized to rabeprazole or placebo for 10 weeks. At the end of 10 weeks, exercise testing was repeated.

RESULTS

A total of 31 patients completed the study (20 asthmatics, 11 non-asthmatics). Twenty-two out of 30 (73%) subjects had abnormal pH studies. For all subjects, rabeprazole improved symptoms more than placebo (P = 0.03). The association was stronger in the pH-positive group (P = 0.009).

CONCLUSION

Acid reflux is common in ETA patients. Many patients with exercise-related respiratory symptoms are misdiagnosed as chronic asthmatics. Exercise-related symptoms improve with the use of acid suppression. This study suggests that ETA patients may benefit from acid suppression.

Further evidence for the role of genes on chromosome 2 and chromosome 5 in the inheritance of pulmonary function

The spirometric measurements FEV1, FVC, and the ratio FEV1/FVC are used in the diagnosis of lung function disorders. Therefore, understanding the genetics underlying these spirometric measurements will increase our knowledge of the genetics of pulmonary function. FEV1 and FVC were measured on 264 members of 26 Utah Genetic Reference pedigrees, originally collected for the Centre d'Etude du Polymorphisme Humain genetic mapping project. Using segregation analysis, we inferred major locus inheritance of the FEV1/FVC ratio, although we could not distinguish between a dominant or recessive mode of inheritance. No evidence of major locus inheritance was found for either FEV1 or FVC. Suggestive evidence of linkage for the ratio FEV1/FVC was found on chromosome 2 (heterogeneity lod = 2.36, dominant model) and chromosome 5 (heterogeneity lod = 2.23, recessive model), replicating linkages from other studies. In addition, nonparametric variance component linkage analysis showed linkage of FEV1/FVC in both of these regions, providing further support to the results. No nonparametric lod scores over 1.5 were obtained for either FEV1 or FVC.

Lack of effect of Rhodiola or oxygenated water supplementation on hypoxemia and oxidative stress

OBJECTIVE

This study investigated the effects of 2 potentially "oxygen promoting" dietary supplements on hypoxia and oxidative stress at a simulated altitude of 4600 m.

METHODS

Fifteen volunteers (ages 20-33) received 3 separate 60-minute hypoxic exposures by breathing 13.6% oxygen at an ambient barometric pressure of 633 mm Hg (simulating the partial pressure of oxygen at 4600 m elevation). Each subject received, in random order, treatments of a 7-day supply of placebo, Rhodiola rosea, and an acute dose of stabilized oxygen dissolved in water. Arterialized capillary blood oxygen samples (PcO2) were measured at baseline and at 30 and 60 minutes of exposure. Pulse oximeter oxyhemoglobin saturation (SaO2) was measured at baseline and at every 10 minutes of hypoxic exposure. Oxidative stress markers measured included baseline and 60-minute exposure serum lipid peroxides (LPO) and urine malondialdehyde (MDA).

RESULTS

For each treatment group, PcO2 decreased by approximately 38% from baseline to 60-minute hypoxic exposure. Similarly, SaO2 also decreased among groups from approximately 97 to 81%. Serum lipid peroxides increased significantly in the placebo group and decreased significantly from baseline in response to the stabilized oxygen treatment (P = .02); there was a trend for decreased LPO with the Rhodiola treatment (P = .10). There were no significant changes for MDA among groups.

CONCLUSIONS

The 2 dietary supplements investigated did not have a significant effect on blood oxygenation after 60 minutes of sedentary hypoxic exposure. Hypoxia-induced oxidative stress was observed in the control group only. Both supplements appeared not to increase oxidative stress and may decrease free radical formation after hypoxic exposure compared with the control.

Chronically inhaled salmeterol improves pulmonary function in heart failure

Inhaled beta-agonists are commonly prescribed for the symptoms of exercise intolerance in heart failure despite a paucity of data regarding their safety and efficacy. This was a prospective, randomized, double-blind, double-dummy, placebo-controlled 14-day cross-over study to determine if chronic inhaled salmeterol therapy 84 microg every 12 hours improved pulmonary function without augmentation of neurohormonal systems or ventricular ectopy in 8 symptomatic heart failure subjects with left ventricular ejection fraction (LVEF) <40% and FEV1 <or=80%. The primary endpoint was FEV1, and the secondary endpoints were forced vital capacity (FVC), forced expiratory flow (FEF25-75), peak expiratory flow rate (PEFR), blood pressure, heart rate, rate-pressure product, plasma norepinephrine, plasma epinephrine, plasma renin activity, percent ventricular ectopy, and salmeterol pharmacokinetics. Salmeterol was associated with a significant 6% improvement in FEV1 compared with placebo (salmeterol 2.46 +/- 0.73 vs. placebo 2.33 +/- 0.73 L, p = 0.01). There was no significant difference in FVC, FEF25-75, and PEFR. Salmeterol increased mean rate-pressure product by 5% (salmeterol 8878 +/- 1560 vs. placebo 8414 +/- 1440 bpm x mm Hg, p = 0.04), although no increase in plasma norepinephrine, epinephrine, plasma renin activity or ventricular ectopy was detected. The Tmax, Cmax, and half-life of salmeterol at steady-state were 5 min, 715 pg/ml and 11.4 hours, respectively. Inhaled salmeterol significantly improves FEV1 without producing measurable effects on neuroactivation or ventricular ectopy. Inhaled salmeterol causes minor increases in rate-pressure product, whose clinical significance remains to be determined. The plasma half-life of salmeterol may be prolonged in heart failure patients, thus leading to accumulation at steady-state.

Oxygen saturation in adult cystic fibrosis patients during exercise at high altitude

The objective of this study was to determine the frequency and severity of decreased arterial oxy-hemoglobin saturation during exercise in adults with cystic fibrosis at 1,500 m above sea level. A convenience sample of 50 adults with cystic fibrosis who did not have hypoxemia (oxygen saturation, < 90%) at rest were evaluated. Spirometry was performed according to American Thoracic Society standards, and maximal exercise tests were performed on an electronically braked cycle ergometer using a ramp protocol individualized for each patient. Pulse oximetry was measured every 2 min. When exercising at high altitude, 45 of 50 patients had a decrease in arterial oxy-hemoglobin saturation from baseline to some degree. In 29 patients, oxy-hemoglobin saturation fell below 90%; in 14 patients, it fell below 85%; and in 4 patients, it fell below 80%. Oxy-hemoglobin saturation decreased to < 90% in 12 of 14 patients with severe pulmonary disease (FEV(1) < 40% predicted), in 15 of 26 patients with moderate disease (40% less than or equal to FEV(1) < 70% predicted), in 2 of 6 patients with mild disease (70% less than or equal to FEV(1) < 90% predicted), and in 0 of 4 with normal pulmonary function (FEV(1) greater than or equal to 90%). Percent predicted FEV(1) (r = 0.57; P < 0.0001) and FEV(1)/FVC ratio (r = 0.52; P < 0.0001) most highly correlated with arterial oxy-hemoglobin saturation at peak exercise. We conclude that at 1,500 m above sea level, adult CF patients with obstructive airways disease are at significant risk for decreased arterial oxy-hemoglobin saturation during exercise. A supervised exercise test should be considered prior to recommending an exercise program for such patients.